"I'm very determined: I'm going to get justice for my mother. I don't care how long it takes or who I have to fight for it," says Celia Peachy, the daughter of Maria Stubbings.

But then her voice cracks and her composure dissolves.

"I found out how my mother died by reading the front page of the local newspaper," she whispers. "The police apologised, but they're sorry about a lot of things and that doesn't really cut it when you lose your mum. On so many occasions the police could have done their job properly or with integrity, and they failed every time."

It is almost two years since Stubbings, aged 50, was murdered by Marc Chivers, her former boyfriend, in her home in Chelmsford, Essex.

A week before her death, she had told the police she feared for her safety. But a litany of mistakes and failures meant help didn't arrive and Chivers, already a convicted killer, was free to strangle the mother-of-two with a dog lead then leave her body in her downstairs toilet.

Yesterday, the Independent Police Complaints Commission published the findings of its two-year investigation. Although it criticised Essex police for its handling of the case, the Stubbing family say they are "bitterly disappointed" by the main focus of the report, which calls for greater controls on criminals who have committed offences abroad.

"We're very angry," says Peachy. "After two years, and who knows what cost to the taxpayer, this report doesn't address the crux of the issue. The hypothetical question of whether the law needs changing is a separate issue.

"The point is that the police had the information and the ability to prevent my mother's murder and they failed to act. It seems like a convenient excuse to blame a law that didn't exist. What's at issue here are their catastrophic failings, the hideous mistakes they made and the complete lack of commonsense they displayed when someone who had already been assaulted by a convicted murderer was begging for their help."

Stubbings met Chivers in 2008. Unknown to her, the 42-year-old had recently been deported to England after serving 15 years of a life sentence in Germany for murdering a former partner. The information was on the national police database but Essex police did not inform Stubbings of the potential danger until after Chivers had assaulted her and was in jail waiting trial.

In October 2008, Chivers pleaded guilty to the assault at Chelmsford crown court and was sentenced to four months, minus time spent on remand.

A panic button was installed in the Stubbings home but was deactivated when Chivers was released, even though he immediately began trying to persuade Stubbings to take him back.

On 11 December, Stubbings called the police to report a break-in. She said she believed it was Chivers. The next day, the police found Richard, Stubbings' 15-year-old son, in a car with Chivers and returned him home, at which point Stubbings made it clear how scared she was of Chivers.

The day afterwards, the police phoned Stubbings to talk about the burglary. Finding her uncommunicative and suspecting Chivers was in the house, they visited her at home. Their notes say she appeared calm but refused to let them in. Instead of investigating further, however, they asked her to sign a document dropping her complaint of burglary and went away.

Soon after, Richard went to the house to look for his mother. At the time, he told Manuel Fernandez, Stubbings's brother, that Chivers had behaved strangely, following him from room to room "like a shadow".

The family are convinced Stubbings was already dead at this point.

"Had Richard wanted to use the downstairs toilet, he would have found the body of his mother lying flung underneath a pile of coats – and then he would probably have joined her there," says Fernandez. "He knows that and it haunts him. He knows he could have died that day."

It wasn't until 18 December that a senior officer questioned why the case hadn't been followed up and the police returned to the home. Chivers opened the door and told them Stubbings wasn't in but, instead of searching the house, the police accepted his word and went away. The body was discovered the next day after the police returned.

The family say they will take legal action against the police.

Sandra Horley, chief executive of Refuge, which has been supporting the family, said that she is "staggered by the inadequacy of Essex police.

"Essex police, and sadly many other forces around the country, are simply not taking domestic violence seriously," said Horley. "Two women are killed every week in the UK by a current or former partner. The domestic homicide rate actually increased last year by 42%. How many more Marias must die?"

• This article was amended on 8 December 2010 to clarify details of where the body was left